This invention relates to condensation copolymer preparation, and more particularly to the preparation of copolymers of polyether polymers and oxycarbonyl group-containing polymers.
Polycarbonates, polyarylates, polyethersulfones, polyetherketones, and polyetherimides (the latter three frequently being collectively designated xe2x80x9cpolyether polymersxe2x80x9d herein) are known high performance polymers characterized by various desirable properties. It is frequently of interest to combine these properties. Combined properties can often be attained by forming blends of two polymers. However, polycarbonates and polyarylates are typically incompatible with most polyether polymers, forming poorly dispersed blends which may be opaque and unsatisfactory for such applications as glazing and fabrication of optical disks.
Therefore, the preparation of copolymers containing both ether-derived and carbonate or ester structural units is of interest. Methods for preparation of such copolymers are hard to develop, since the preparation methods characteristic of each type of polymer are widely different. Polycarbonates are conventionally produced from bisphenols either by reaction with phosgene in a two-phase organic-aqueous system under basic conditions or by reaction with diphenyl carbonate in the melt, and polyarylates are produced under similar conditions. Polyether polymers, on the other hand, are frequently produced by reaction between a salt of a dihydroxyaromatic compound and a dihaloaromatic compound under anhydrous conditions in a dipolar aprotic solvent or a water-immiscible aromatic solvent of low polarity. None of these methods of preparation can be used for both polycarbonates or polyarylates and polyether polymers.
A method of copolymer preparation has been described by McGrath et al. (Polymer Engineering Science, vol. 17, pp. 647-651, 1977) in which hydroxy-terminated polyethersulfone oligomers are first synthesized in a dipolar aprotic solvent. Said oligomers are then isolated and employed in an interfacial reaction with a monomer such as bisphenol A, in a halogenated solvent such as methylene chloride. This synthesis requires two successive, different polymerization reactions under widely different conditions and is thus cumbersome.
It would be more practical to conduct both steps, i.e., the preparation of the polyether oligomers and their reaction to form polycarbonate or polyarylate copolymers, in a single solvent. In addition, low to medium molecular weight hydroxy-terminated polyether oligomers are useful to make short-block, random, block copolymers, which do not exhibit complex multi-phase morphology often observed for long-sequence block copolymers.
Copolymer and oligomer preparation has not been readily achievable, however, by reason of differences in solubility between an alkali metal salt of the dihydroxyaromatic compound and the dihaloaromatic compound, as illustrated by bis(4-chlorophenyl) sulfone. In a homogeneous solution polymerization, such as the procedure in dipolar aprotic solvents, hydroxy-terminated polyether oligomers with statistically distributed molecular weight can be readily prepared simply by use of an excess of the dihydroxyaromatic compound. However, it is not possible to make such oligomers of low to moderate molecular weights in non-polar solvents, even when phase transfer catalysts are employed. This is true because the alkali metal (e.g., sodium) salt of the dihydroxyaromatic compound is typically insoluble in relatively non-polar solvents such as anisole and dichlorobenzene. In the presence of phase transfer catalyst, a minute amount of the salt may be solubilized at any moment. As the solubilized salt reacts with the dihaloaromatic compound in solution, more salt dissolves to maintain its minute steady state concentration. At the end of the reaction, when all the dihaloaromatic compound is consumed, the excess salt is left undissolved without participating the polymerization reaction. Thus, despite use of excess dihydroxyaromatic compound the system behaves like an equimolar polymerization, resulting in high molecular weight polymer.
It is of interest, therefore, to develop a simple method for the synthesis of highly random polyether-polycarbonate and polyether-polyester copolymers. It is also of interest to develop a method for preparing and isolating low to medium molecular weight hydroxy-terminated oligomers of the polyether polymers, rather than producing only high molecular weight polymers.
The present invention is based in part on the discovery that when polyether polymers are prepared in relatively non-polar solvents in the presence of polycarbonate or a polyarylate, extensive exchange takes place with incorporation of carbonate or arylate units in the product polymer in relatively random fashion.
The invention in one of its aspects, therefore, is a method for preparing a copolymer of a first polymer which is a polyethersulfone, polyetherketone, or polyetherimide and a second condensation polymer characterized by structural units containing an oxycarbonyl group, which comprises contacting, under reactive conditions, at least one salt of a dihydroxyaromatic compound with at least one substituted aromatic compound of the formula
Z(A1xe2x80x94X1)2,xe2x80x83xe2x80x83(I)
wherein Z is an activating radical, A1 is an aromatic radical and X1 is fluoro, chloro, bromo or nitro, in the presence of said second polymer.
It has further been discovered that the product copolymers can be degraded by saponification into hydroxy-terminated oligomers of the polyether polymers. Said oligomers are capable of conversion into special purpose copolymers, such as optical grade copolyethercarbonates, by means of an interfacial polymerization in the same vessel or by addition to a melt polycarbonate preparation mixture.
Another aspect of the invention, therefore, is a method for preparing at least one hydroxy-terminated oligomer of a polyether polymer which comprises preparing a copolymer as described above and contacting said copolymer with alkali metal hydroxide under reactive conditions, thus hydrolyzing carbonate and ester units.